Threaded plastic closures used on containers to form packages for carbonated beverages, or otherwise pressurized products, have met with very widespread success in the marketplace. Packages of this nature typically include a closure including a molded plastic closure cap having a top wall portion, and an annular, dependent cylindrical skirt portion. The skirt portion typically includes an internal thread formation configured for thread cooperation with alike external thread formation on the associated container. The desired sealing with the container can be achieved by providing the closure with a sealing liner positioned generally adjacent the top wall portion. Closures of this type which have proven to be particularly commercially successful are disclosed in U.S. Pat. No. 4,343,754, U.S. Pat. No. 4,378,893, and U.S. Pat. No. 4,497,765, all of which are hereby incorporated by reference. For many applications, it is desirable to configure such closures for tamper-indication, such as in accordance with the teachings of the above-referenced U.S. Pat. No. 4,497,765, or in accordance with the teachings of U.S. Pat. No. 4,938,370, U.S. Pat. No. 4,978,017, and U.S. Pat. No. 5,004,112, all hereby incorporated by reference.
As noted, packages of the above-type have proven to be very commercially successful for containing carbonated contents. As such closures of this type are typically configured to facilitate venting and release of gas pressure from within the container during closure removal. In particular, it is desirable to release the gas pressure from within the container prior to disengagement of the closure thread formation from the threads provided on the neck portion of the associated container.
Heretofore, to facilitate the release of gas pressure from within such a package, both the internal thread formation of the closure, and the associated external thread formation of the container, are provided with a plurality of axially extending vent grooves, which traverse and substantially interrupt the respective thread formations. By such arrangements, gas from within the package can readily flow through the vent grooves attendant to release of the closure's seal, but prior to disengagement of the respective thread formation.
Recognizing that release of gas pressure from within a package having pressurized contents is dependent upon various factors, including the pressure and volume of gas within the package, experience has shown that it can be desirable to provide one or more rotation-inhibiting projections, such as on the closure of the package, for inter-engagement with the thread formation and vent grooves of the associated container. Such projections, sometimes referred to as “speed bumps”, frictionally engage the container finish during closure removal to inhibit free rotation of the closure with respect to the container, thus facilitating release of gas pressure from within the package prior to disengagement of the respective thread formation.
While the provision of such rotation-inhibiting projections has become widespread for packages for carbonated beverages and the like, it is nevertheless desirable that plastic closures for such packages do not require relatively high levels of applied torque for removal, thus facilitating convenient manipulation and removal by consumers. Recognizing that such “removal torques” be kept desirably low, efforts have been made to configure rotation-inhibiting projections to provide the desired rotation-inhibiting effect, without undesirably contributing to high removal torques for closure removal. As will be recognized by those familiar with the art, closure designers must consider the removal torques which are ordinarily necessary for overcoming the static and dynamic friction which exists between the sealing portion of the closure and the associated container, and for overcoming the friction between the closure and container thread formations, as well as the torque which must be applied for effecting fracture or other visually discernible evidence of opening by operation of the tamper-indication feature of the package.
U.S. Pat. No. 6,123,212, hereby incorporated by reference, illustrates an arrangement of rotation-inhibiting projections for a closure which facilitates high-speed application, while providing the desired rotation-inhibiting effect to facilitate release of gas pressure from within a package having pressurized contents. The present invention seeks to provide an improved arrangement of tamper-inhibiting projections which facilitate the desired release of gas pressure, while desirably acting to minimize removal torques, thus facilitating convenient manipulation and removal of closures by consumers.